I think I will make such device too. Do you have any licensing policy?
My main problem is getting latex 10mm tube. Is there any internet shop with it? I have found something here but the prices are insane...
Regards
Michal

I think I will make such device too. Do you have any licensing policy?
My main problem is getting latex 10mm tube. Is there any internet shop with it? I have found something here but the prices are insane...
Regards
Michal

It's the simplicity which makes it so genious. A very convincing concept and build!

Question: You've made kind of 'clamps' around the wing. Is this to prevent the wing from pitching up upon launch? Or would a 90 degree upwards pointing pusher at the lower end suffice as well?
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Yes its stops the wing from pitching up or possibly even flipping over backwards because its getting pushed from way behind its CG.

Quote:

Originally Posted by kist2001

With increasing tension your gantry is going to always slam into the end of your launcher. May I suggest you lengthen the launcher and put the attachment point for the bands about 1.5 foot back and looped underneath. Thus when the plane launches the bands will self brake the gantry,

Thanks for the idea. Simplicity was key in this build and it had to be short enough to fit in my car. Yes it does hit the end with knock but there is sufficient rubber damping. The sudden stop also helps dislodge the plane from carriage.

Quote:

Originally Posted by tty044

I think I will make such device too. Do you have any licensing policy?
My main problem is getting latex 10mm tube. Is there any internet shop with it? I have found something here but the prices are insane...
Regards
Michal

Go ahead and build as many as you want. I get my Latex tubing from a local supplier. The stuff they sell on HK should work fine.

I have made some guesses and posted my shopping list below, If anyone has time I wonder if anyone could look at the items and ensure they are good enough for the job? The one piece i have left off is the bent aluminium cradle that the plane sits in.....Thanks, rich

I have made some guesses and posted my shopping list below, If anyone has time I wonder if anyone could look at the items and ensure they are good enough for the job? The one piece i have left off is the bent aluminium cradle that the plane sits in.....Thanks, rich

Hi Bret, cheers for confirming my questions, unfortunately I didnt get any updates from the website to say that anyone had replied! so ordered all the parts above in my shopping list. I am not having much luck with the catapult at the moment. And have made a series of modifications.

1. The toggle clips and the small bits of 20mm alloy riveted to make the joiner didn't work very well for me. So i used a 1 meter piece of wood that fits 500mm inside each half of the boxed alloy. However it is 1mm smaller and the rail doesn't line up nicely, the bearings dont run smoothly over the join, and have begun cutting into the rail :-(. May need to rethink how to do the joiner.

2. the rear bearings kept coming off the rail. Possibly to the holes in the plate not being drilled as accurately as I would have liked. So i have added a second plate underneath to ensure the bolts don't bent outwards causing the carrier to come off the rail. This works well.

3. Due to the fact that i had to add a piece of wood inside the rail, i had to remove the release tube that flxes to release the pin. I halved the length of this and put a bolt

4. I initially thought a pulley system would work well with HobbyKing 8mm Silicon Rubber Bungee Hi-Start Cord. So started with 2 lengths 1m long, tied to base of catapult, then moved up and around the pulleys, and fixed onto the carriage, this didn't provide anywhere near enough pull. So replaced it with hardware store bungee chord. Which has more pull, but still didn't provide enough power. As seen in the first launch.

I then ditched the pulley system, and simply used two loops of bungee, this gave enough power to just about launch the plane, however in the video below, the plane does launch, but you see the carrier slow down considerably about half way along the rails. I think it's important for it to keep pulling all the way to the end.

On the third launch i applied full throttle as i stepped on the release pin. I'd rather not apply throttle until the plane has left the launcher to avoid prop strikes, certainly for the next few tests anyway.

I'm not sure which bungees to use to get enough pull to launch the plane off properly. I have drawn a picture showing my thoughts, using two pulleys, and two loops of bungee chord - My question is why do you think i need so much extra chord to launch a plane that is half the weight of the x8?

4. I initially thought a pulley system would work well with HobbyKing 8mm Silicon Rubber Bungee Hi-Start Cord. So started with 2 lengths 1m long, tied to base of catapult, then moved up and around the pulleys, and fixed onto the carriage, this didn't provide anywhere near enough pull.

I´m shocked . I ordered the same 8mm Silicon Rubber Bungee Hi-Start Cord (its still on the way).
Do you mean, your "unstretched" cord is 1m long (one way, the half way of your launcher)???
Bretts cords seem to be around 25% of the launcher lenght, see the picture below (I love to cut scenes from clips and add measurements ). The cord will streched about 4 times of its original lenght.
Brett, please correct me if I'm wrong.